Tortoise shells have been sculpted over time to help the animal get back on its feet if it gets into trouble. They also acts as armour and help their reptilian inhabitants retain heat.
It took two mathematicians more than five years to design the world’s first truly self-righting shape before they realised nature had beaten them to it by several million years. The gomboc is a curved shape that can only rest of one surface, but it isn’t weighted. Purely the shape of the object causes it to rest on the same face each time.
Tortoises always end up back on their feet, and many species are shaped with the same properties at the self-righting gomboc. Tortoises with tall shells, like the Indian star tortoise have the best shells for finding their feet, and flatter shelled species have to use their necks to prop themselves back up.
The shell also acts as a natural shield to protect against predators, and it can even act as a heater to warm the tortoise up when it’s cold. Overall, tortoises are better off with their shells and might be lost without them.
Image from www.flickr.com/photos/kuribo